Maybe for some, but there are other reports like this one where there is tons of free ram. I saw a few posts somewhere where people have even reset the arc to default 50% and the problem still occurs. The thread below has several examples which indicate a different issue perhaps, but still manifests in the UI. Hopefully they can find the issue(s).
That’s why I never install a .0 release!
https://forums.truenas.com/t/very-slow-webui-login-apps-etc-scale-dragonfish-rc